<wicket:panel xmlns:wicket="http://wicket.apache.org">
    <form wicket:id="prj">
        Num. Colli per 1 Collo free:<input wicket:id="numberOfItemsPerFreeProduct" class="inp-form-xsmall"/>
        <input wicket:id="submit" value="salva progetto" type="submit" />
    </form>
</wicket:panel>